There's now an explanation from the Office of Personnel Management on how members of Congress and much of their staff will get their health insurance starting next year.

At issue is a tiny provision of the health overhaul law that caused a large stir on Capitol Hill. It required all members of Congress and much of their staff to give up their federal worker health insurance as of the end of 2013 and begin taking part in the Obamacare health insurance exchanges instead.

What was unclear, however, at least until last week, is whether those 11,000 or so people would be able to continue receiving the same employer contribution to their health insurance — some 75 percent of the cost of coverage — as the rest of the federal workforce.

After some apparently high level intervention (President Obama himself promised senators in a closed door meeting he was working on the issue), White House officials confirmed last week that yes, those who switch to exchange coverage will be able to continue to receive government insurance contributions towards that coverage.

"The amount of the employer contribution for Members of Congress and official staff will be the same as for other Federal employees," said a question-and-answer document issued by OPM.

But the rule declined to make another key determination: exactly who among the 20,000 or so Capitol Hill workers will have to drop their federal coverage and switch to the exchanges.

According to the health law, those required to make the switch are "all full-time and part-time employees employed by the official office of a member of Congress." Most people had been interpreting that as excluding those working for House and Senate committee and leadership offices.

OPM, however, said that "Because there is not an existing statutory or regulatory definition, OPM believes Congress is best able to make the determination as to whether an individual is employed by the 'official office' of the Member of Congress."

Under the proposed rule, most years Congress will have to make that determination by October. This year, however, members will have an additional 30 days to decide who gets what kind of coverage.

Not everyone is satisfied with the solution, however. Policy analysts from the Heritage Foundation, who argued in a paper last week that the administration lacked the authority to make any kind of fix to the congressional coverage glitch, say the new rules are plainly beyond what is legal for the administration to propose.

"It was bad enough the Congress had to pass the law to find out what was in it," wrote Edmund Haislmaier in a post on the Heritage website. "Now the Administration is ignoring the law when they don't like what they find."